Oxidation of oleuropein studied by EPR and spectrophotometry

The autoxidation at alkaline pH and enzymatic oxidation by mushroom tyrosinase of oleuropein, the dominant biophenol present in the fruits and leaves of Olea europea, was followed by both electron paramagnetic resonance (EPR) and absorption spectroscopy. For comparison, the same oxidation processes were applied to 4‐methylcatechol, a simple polyphenol present in olive mill wastewaters. EPR spectra of stable o‐semiquinone radicals produced during autoxidation at pH 12 and short‐lived o‐semiquinone free radicals produced during autoxidation at pH 9.0 or tyrosinase action and stabilized by chelation with a diamagnetic metal ion (Mg²⁺) were recorded for both polyphenols, and the corresponding hyperfine splitting constants were determined. The UV‐Vis spectral characteristics of the oxidation of polyphenols were highly dependent on the type of polyphenol, oxidant type and the pH of the reaction. The kinetic behavior of tyrosinase in the presence of oleuropein and 4‐methylcatechol was followed by recording spectral changes at 400 nm (absorption maximum) over time. The tysosinase activity with oleuropein showed a pronounced pH optimum at pH 6.5 and a minor one around pH 8. From the data analysis of the initial rate at pH 6.5, the kinetic parameters K_m = 0.34 ± 0.03 mM and V_max = 0.029 ± 0.002 ΔA₄₀₀ min^–1 were determined for oleuropein.     

Public-Private Partnerships in the Water Sector

Abstract

Types of partnerships between public and private companies in water and sewage services are evaluated on the basis of the economic efficiency of the scheme for each partner. Modeling of public-private partnerships involves the formulation of a contract prototype, which determines the roles, functions, and responsibilities as well as the allocation of costs and revenues for each partner. Alternative water management scenarios are used to identify the investments required for meeting the projected demand for water and sewage services. Investment and operational costs as well as revenues from water and sewage services are estimated according to the allocation defined in the contract prototype. The economic efficiency of the scheme is assessed through a cost benefit analysis for each partner. The evaluation of different water management scenarios indicates that, for the Cyclades Islands, Greece, there is a substantial water market where several forms of partnerships could be attractive for both the public and the private sectors. Such partnerships include, among others, lease purchase, temporary privatization, built operate transfer (BOT), and built own operate transfer (BOOT). These forms of public-private partnerships could also be successful in similar regions where significant improvements and expansion of the infrastructure is required while access to the required funds and expertise is restricted for small public water companies.     

School-screening for scoliosis. A prospective epidemiological study in northwestern and central Greece

A two-year prospective study was done to assess the prevalence and distribution of various parameters associated with scoliosis in schoolchildren in northwestern and central Greece. A total of 82,901 children (41,939 boys and 40,962 girls) who were nine to fourteen years old were screened for scoliosis. Five thousand eight hundred and three children had clinical signs of scoliosis and, of these, 4185 were referred for posteroanterior radiographs (to be made with the patient standing) because they had a positive result on the forward-bending test (a difference of more than five millimeters between the two sides of the torso as measured in the thoracic or thoracolumbar region with use of a ruler and a level plane) at the time of a second screening. The prevalence of scoliosis (defined as a curve of 10 degrees or more) was 1.7 per cent (1436 of 82,901 children), and most of the curves (1255; prevalence, 1.5 per cent) were small (10 to 19 degrees). The ratio of boys to girls was 1:2.1 over-all but varied according to the magnitude of the curve (1:1.5 for curves of less than 10 degrees, 1:2.7 for curves of 10 to 19 degrees, 1:7.5 for curves of 20 to 29 degrees, 1:5.5 for curves of 30 to 39 degrees, and 1:1.2 for curves of 40 degrees or more). Thoracolumbar curves were the most common type of curve identified, followed by lumbar curves; specifically, of the 1436 children who had a curve of at least 10 degrees, 493 (34.3 per cent) had a thoracolumbar curve, 475 (33.1 per cent) had a lumbar curve, 261 (18.2 per cent) had a thoracic curve, and 207 (14.4 per cent) had a double curve. Although most (753) of these curves were to the left, the left:right ratio varied according to the location of the apex of the curve (1:3.1 for thoracic curves, 2.0:1 for thoracolumbar curves, and 3.2:1 for lumbar curves). The cost of the screening process was negligible (estimated at thirty cents per child); however, the decreased number of operative procedures performed in children from the geographical area of our University Hospital, the identification of a large number of previously undiagnosed curves (eleven of which were treated operatively and 170 of which were treated with a brace), and the identification of children who were at high risk for progression were considered important benefits of the school-screening program.     

Water demand management: implementation principles and indicative case studies

Current practices for the efficient use and management of water resources are based on the conjunctive application of water supply and demand measures. Even though options for the augmentation of water supply are widely analysed and assessed, water demand management remains an open field for study, as it is highly dependent on the socio‐economic features of a region and has a site‐specific character. This paper summarizes the guiding principles of demand management and presents some successful application examples of demand management measures from regions that cover a wide range of socioeconomic and environmental conditions in an effort to identify the critical factors for the efficient planning and implementation of demand management plans.     

Multi-parameter performance analysis for decentralized cognitive radio networks

In this paper, we investigate the impact of primary user activity, secondary user activity, interface switching, channel fading and finite-length queuing on the performance of decentralized cognitive radio networks. The individual processes of these service-disruptive effects are modeled as Markov chains based on cross-layer information locally available at the network nodes. A queuing analysis is conducted and various performance measures are derived regarding the packet loss, throughput, spectral efficiency, and packet delay distribution. Numerical results demonstrate the impact of various system parameters on the system performance, providing insights for cross-layer design and autonomous decision making in decentralized cognitive radio networks.     

Miscibility behavior and formation mechanism of stabilized felodipine-polyvinylpyrrolidone amorphous solid dispersions

In the present study, solid dispersion systems of felodipine (FEL) with polyvinylpyrrolidone (PVP) were developed, in order to enhance solid state stability and release kinetics. The prepared systems were characterized by using Differential Scanning Calorimetry, X-Ray Diffraction, and Scanning Electron Microscopy techniques, while the interactions which take place were identified by using Fourier Transformation-Infrared Spectroscopy. Due to the formation of hydrogen bonds between the carbonyl group of PVP and the amino groups of FEL, transition of FEL from crystalline to amorphous state was achieved. The dispersion of FEL was found to be in nano-scale particle sizes and dependent on the FEL/PVP ratio. This modification leads to partial miscibility of the two components, as it was verified by DSC and optimal glass dispersion of FEL into the polymer matrix since no crystalline structure was detected with XRD. The above deformation has a significant effect on the dissolution enhancement and the release kinetics of FEL, as it causes the pattern to change from linear to logarithmic. An impressive optimization of the dissolution profile is observed corresponding to a rapid release of FEL in the system containing 10% w/w of FEL, releasing 100% in approximately 20 min. The particle size of dispersed FEL into PVP matrix could be classified as the main parameter affecting dissolution optimization. The mechanism of such enhancement consists of the lower energy required for the dissolution due to the amorphous transition and the fine dispersion, which leads to an optimal contact surface of the drug substance with the dissolution media. The prepared systems are stable during storage at 40 ± 1°C and relative humidity of 75 ± 5%. Addition of sodium docusate as surfactant does not affect the release kinetics, but only the initial burst due to its effect on the surface tension and wettability of the systems.     

Partial purification and characterization of peroxidase from olives (<Emphasis Type="Italic">Olea europaea</Emphasis> cv. Koroneiki)

The enzyme peroxidase (POD) activity was extracted from olives (Olea europaea cv. Koroneiki) and was partially purified by ammonium sulfate fractionation and gel permeation chromatography (Sephacryl S 300). Further characterization of the POD was performed using the ammonium sulfate purified fraction. POD showed a molecular mass of 44 ± 2 kDa and it expressed catalytic activity with 2,2′-azino-bis(3-ethylbenz-thiazoline-6-sulfonic acid) (ABTS), N,N-dimethyl-p-phenylenediamine (DMPD) and some olive fruit phenols. However, the enzyme was found ineffective as regards the oxidation of oleuropein, the major polyphenol of olives, as well as with coumaric, ferulic, ascorbic and p-hydroxy benzoic acids. pH optimum of the peroxidase-catalyzed oxidation depended on the substrate used and it varied from 4.0 to 6.0. Olive peroxidase shows high thermal stability. Oleuropein, the major polyphenol of olives, drastically inhibited ABTS peroxidation by the POD preparation with an IC₅₀ value of 47 μM. The presence of POD enzyme activity in virgin olive oil samples was also confirmed.     

Vascular complications in orthopaedic patients treated by orthopaedic microsurgeons

Over a 20 year period, five patients experienced serious vascular complications involving major arterial insult during various routine orthopaedic procedures. The nature of the vascular damage necessitated immediate surgical repair which was performed successfully by an orthopaedic microsurgeon who was either a member of the initial surgical team or the hospital's Orthopaedic Unit. The purpose of this study is to illustrate not only the severity of these limb and/or life-threatening complications, but also to focus attention on the importance of the orthopaedic surgeon's ability to manage these serious injuries promptly. This suggests the need for Orthopaedic Units to have surgeons with adequate training in microvascular techniques, so as to be able to successfully manage these unexpected and serious complications. We conclude that the presence of a vascular surgeon or an orthopaedic surgeon trained in microvascular surgery represents an invaluable attribute to the orthopaedic team, and minimizes, if not eliminates the potentially disastrous outcome from these serious intraoperative vascular complications.     

Development and characterization of a digestion model based on olive oil microemulsions

Olive oil microemulsions were used as biomimetic model to simulate aspects of the digestion process in the small intestine. Hydrolytic activity of trypsin and alkaline phosphatase in microemulsions in the presence and in the absence of squalene and phenolic acids at pH 8.5 and 37°C was examined. In the case of trypsin kinetic constants were calculated and found K_m = 0.080 ± 0.002 mM and V_max = 3.8 × 10^?5 ± 0.06 × 10^?5 mM/s. When gallic acid and squalene were added, hydrolytic activity of trypsin was reduced to 77 ± 2% and 69 ± 3%, respectively. In the presence of o‐, m‐, and p‐coumaric acid, protocatechouic acid, and caffeic acid, enzymatic activity was increased up to 142 ± 6%. Hydrolytic activity of alkaline phosphatase was inhibited in the presence of squalene and phenolic acids. To evaluate the size of the dispersed aqueous droplets in the presence and in the absence of enzymes, substrates, and antioxidants, dynamic light scattering (DLS) measurements were carried out and diameters in the range of 8.9–13.4 nm were observed. Membrane flexibility and micropolarity were studied by electron paramagnetic resonance (EPR) spectroscopy. Rotational correlation time (τ_R), order parameter (S), and hyperfine splitting constant (A₀) of doxyl stearic acid in the microemulsions were calculated and found 2.06 ns, 0.17, and 14.30 G, respectively. These values were slightly affected in the presence of additives. Practical applications: The main aim of the present study is to enhance our understanding on the digestibility of proteins and lipids in the presence of food antioxidants suggesting an in vitro digestion model for hydrolases based on virgin olive oil microemulsions. The information generated in this study could potentially facilitate the design and development of novel functional food formulations based on food‐grade colloidal delivery systems. Since modification or fortification of different food products focusing on different areas of health concern are of growing interest among the various sectors of food industry, the proposed research results could be of particular interest.     

The presence of oxidizing enzyme activities in virgin olive oil

Samples of Greek virgin olive oils were examined for the presence of proteins and oxidative enzyme activities. All oil samples tested contained detectable amounts of protein, as well as lipoxygenase and polyphenol oxidase activities. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and size-exclusion chromatography of olive oil extracts revealed the presence of low-molecular-mass (10–40 kDa) silver-staining and ultraviolet-absorbing components, respectively. Both lipoxygenase and polyphenol oxidase catalytic activities were heat- and protease-sensitive, and they expressed Michaelis-Menten kinetics.